| 摘要 |
PROBLEM TO BE SOLVED: To efficiently process the lower tip of a preform into a good spindle form by fusing a lower part of an optical fiber preform to an upper part of a dummy sphere, pulling the fused material, forming a spindle part in the fused part, then mechanically rotating both or either one thereof so as to produce a difference in extent of rotation in the preform and the sphere and simultaneously pulling a part between both parts. SOLUTION: A dummy sphere 100 is pulled upward and brought near to a lower part of an optical fiber preform 101 under rotating of the same extent of rotation of both, heated and softened with a burner 102. After both are brought into contact, the lifting of the sphere 100 is stopped while maintaining the rotation of the sphere 100 constant and then slowly lowered to pull a part between both and form a spindle part in the tip 101A of the lower part of the preform 101. The torque of the sphere 100 is suppressed for the torque of the preform 101 to apply a force in the prescribed direction of reverse rotation to the sphere 100 to form a twisted part between the tip side of the lower part of the preform 101 and the tip side of the upper part of the sphere 100, which is then lowered to twist off the dummy sphere 100 in the constricted part below the spindle part. |
